A mast which can be erected by withdrawing elements from a magazine and inserting these elements into a mast structure is disclosed in Swiss Patent 431,917.
The individual elements of this mast are tubular or rod-shaped and are formed at their opposite ends with complementary form-locking elements enabling successive elements to engage one another.
The extension of the mast is effected by inserting one element after another into previously positioned elements and, for this purpose, the mast comprises a lifting unit, an individual magazine containing the element and a device connected to that magazine for feeding the mast elements into the lifting unit. The lifting movement is effected by a lifting cylinder coaxial with the mast structure and located between the base of the mast. The mast is supported by roller bearings into which the elements are fed laterally The mast structure which thus results is limited in diameter and thus is limited in the loads which can be applied thereto.
It will be appreciated that the peak load which can be applied to the top of the mast, the resistance of the mast to bending in general and its static stability are all determined by the minimum diameter of the mast and thus by the minimum diameter of the mast elements making up the mast.
When cylindrical elements are used to assemble the mast and the mast is of large diameter, the individual elements become too heavy to handle with ease and too difficult to assemble in succession. As a consequence, a practical, high load capacity mast which can be assembled from successive elements utilizing these principles has not been realized heretofore.